The invention relates to a control device for camshaft systems of an internal combustion engine with n banks of cylinders arranged in a V-shaped configuration, the control device having a distribution system with a first distributor gear, which intermeshes with an output gear arranged on a crankshaft of the internal combustion engine.
A central output of generic type for an internal combustion engine of a motorcycle is disclosed by U.S. Pat. No. 4,671,223. In this case a straightforward gear drive is produced, a separate distribution system being assigned to each camshaft system of one bank of cylinders. The gears of each distribution system are mounted in a respective frame. The straightforward gear drive has the disadvantage that it generates very loud noise. Furthermore, having a separate output line for each camshaft system makes this arrangement mechanically expensive, and it takes up a lot of space. A central output for the control device of an internal combustion engine for a motor vehicle would not be practically feasible with this system, since all cylinder banks would have to have at least one division. This would lead, however, to considerable mechanical weakening of the engine block, which with the torques and forces occurring in motor vehicles could not be tolerated.
A central control output is furthermore disclosed in the article xe2x80x9cThe Porsche 4.5-liter Racing Sports Car, Type 917xe2x80x9d by H. Metzger, which appeared in the offprint from a German periodical, Automobiltechnische Zeitschrift (ATZ), Vol. 71 No. 9/12/1969, pages 313 to 320 for an air-cooled four-stroke engine with two flat rows of cylinders, which is designed especially for racing purposes. The drive to four camshafts comes from a central output gear on the crankshaft to both rows of cylinders, in each case by way of five straight-toothed gears on needle-roller bearings. In other words, a separate control device is assigned to each row of cylinders. The five gears arranged between crankshaft and each of the camshafts are in each case arranged in a gear housing, which can be bolted to a crankcase. This, too, is a straightforward gear drive, which has the aforementioned disadvantage that it generates considerable noise levels. In the case of a racing car for a Constructors"" World Championship this may not be critical, but for a comfortable motor vehicle for day-to-day use in public road traffic it is unacceptable.
The object of the present invention therefore is to provide a simple control device of the above-mentioned type that takes up little overall space and overcomes the above-mentioned disadvantages.
To this end it is proposed, according to the invention, that the distribution system have m less than n secondary distributor gears, which intermesh with the first distributor gear and transmit a driving force to the n camshaft systems of the n banks of cylinders through n endless-chain drives.
This has the advantage that all camshaft systems of respective cylinders can be driven by a single distribution system proceeding from the middle of the internal combustion engine, for example. This advantageously simplifies the mechanical construction of the control device and reduces the overall space required and the weight.
A particularly space-saving central output for the control device is obtained by arranging the output gear centrally on the crankshaft.
It is advisable if m=nxe2x88x921 or m=nxe2x88x922, it being particularly preferable if n=2, 3 or 4.
For ease of assembly the first and the secondary distributor gears are arranged in a common carrier, which when pre-assembled can be fixed to a crankcase of the internal combustion engine. For example, with a central output for the control device, bolting the carrier onto the crankcase provides additional reinforcement for the engine block, which is actually mechanically weakened by corresponding recesses required for the central output.
Simple assembly of the control device, for example in a recess in a crankcase for a central output, is achieved by providing a module that carries the endless-chain drive between each secondary distributor gear and each camshaft system. The module being pre-assembled so that it carries a chain sprocket, which can be frictionally and coaxially fitted to the respective secondary distributor gear, at one end and at least one camshaft gear on an opposite end, the endless-chain drive passing around the chain sprocket and the camshaft gear.
A suitable transmission ratio between the crankshaft and the respective camshaft system is effectively achieved by selecting a tooth ratio of the secondary distributor gear to the chain sprocket such that a crankshaft to camshaft system transmission ratio of 2:1 is obtained.
Secure guiding of the chain of the endless-chain drive is achieved in that the module has a U-shaped guide plate for the endless-chain drive on the idle strand side.
Reliable, frictional running of the chain of the endless-chain drive with low mechanical wear and low noise is achieved in that the module has a chain-tensioning fixture on the load strand side.